Camera SPD

[Bjenks]

It seems I am getting contradictory advice on surge protection for security cameras mounted on buildings or poles. The job I am working on now has a COAX video feed and 24VAC (I don't see any EGC coming in to the camera). Most SPD companies who address this situation have a device with an IN/OUT BNC and Pos/ Neg. AC connection forming what IEEE calls a Surge Reference Equalizer . Then a big ground lug for connecting to the ?ground.? Typically these cameras are more than 20ft from a GEC.

Here is where I am confused. All of the manufactures I talked to said just run a ground conductor straight down to a ground rod and connect the other end to the ground lug of the SPD. I asked about running a GEC to connect the ground rod to the building GEC and they all said it is not needed. They say this is because there technically isn't a connection to the pole ground rod except during a few nanoseconds of a surge. Would this be a NEC violation of not interconnecting grounding systems or is this different since there normally isn?t a connection? If I also have surge protection where the cables enter the building it looks like article 820 is requiring me to ground the shielding, but I am putting surge protection there and don't believe the SPD will be actually grounding the shield but putting a SPD between it. Is that a violation? Finally, if I do have to interconnect ground rods it seems the requirements of 820 require a #6 connection which doesn?t make sense since the SPD to Rod connection is only #14.

 

[Lcdrwalker]

Try 250.54 and 820.

 

[Bjenks]

I believe 250.54 still requires the aux grounding electrode to be bonded to the EGC. I don't see how there will be a EGC on a camera with only a Hot and Neutral for the power and a COAX cable ran in PVC. But maybe that is good enough and I am over complicating things.:-?

820.100 mentions that grounding of the shield at the entrance Now I understand why the connection between ground rods is #6 while the cable GEC is #14. This is to keep the grounding plane at an equal potential.

I think I am trying to see if there is a way to run SPD to a new ground rod without connecting that new ground rod to another GEC.

 

[tesla fan]

Years ago , I worked for a security company for 10 years, I installed many cctv systems and we used a common fused power supply for the cameras and never used surge protection on the individual cameras. Is this a requirement for your area? If it isnt then its not necessary.

 

[hbiss]

To satisfy the NEC you only need a protector at the building point of entrance. That would be a ground block for the shield of the coax and protection for the two power conductors.

The NEC doesn't care what you provide at the cameras. It would be there only to (possibly) prevent damage to them. There is no life/safety issue.

-Hal

 

[Bjenks]

After removing myself and coming back I know you can't drive a ground rod and connect a surge protection to it even if you are only connecting the equipment ground to the rod during a strike. This would still create a voltage difference between the camera and the head end equipement and could still cause damage.

I have decided to install a gas tube based video only surge protector at the camera that will connect the center to the shield only. Then at the camera hub in each electric room I will do a UPS/Coax/24VAC common ground surge protector that will be wire to the GEC. Then at the DVR in the clubhouse where every building's camera comes back to I will do a UPS/16 port Coax/AC surge protector that will be all tied to the UPS ground. This is all per IEEE Emerald book and NEC except I won't get the best of protection at the camera without the expense of running ground rods that connect to the GEC with #6 which the customer won't spend the money on.

I think I got confused thinking the application guy at these surge protection companies are experts. However, they probably only know the sales literature and company application notes real well.